12 January - 20 June 2016

How processing affects fat absorption from plant-based foods

Research published in the Journal of Functional Foods by researchers from King’s College London, University of Surrey and the University of Messina has reported that the processing process can affect the amount of fat and energy absorbed by the body from plant based food products.

Research published in the Journal of Functional Foods by researchers from King's College London, University of Surrey and the University of Messina has reported that the processing process can affect the amount of fat and energy absorbed by the body from plant based food products.

Whilst almonds have a high lipid content, high consumption has been reported, in randomised control trials, to not increase body weight or BMI. These findings have been thought to be due to almond low lipid bio-accessibility. Bio-accessibility is defined in the current study as "the proportion of a nutrient or phytochemical compound released from a complex food matrix during digestion and therefore potentially available for absorption in the gastrointestinal (GI) tract."

The aim of the current study by Grassby et al. was to assess and compare lipid bio-accessibility from two muffins, one prepared using 85g of almond microparticles (particle size 1700 – 2000 µm) and the other 85g of almond flour (<450 µm). Both muffins had identical nutrient content and, apart from the almonds, used the same ingredients.

Grassby et al. recruited a healthy volunteer for 8 days (4 days for each muffin type).  On each study day the volunteer was instructed to chew half a muffin and custard (used to encourage the volunteer to swallow without significant chewing) and then expectorate when they felt the need to swallow.  The volunteer produced 21.8 g± 4.2 and 35.8g ±3.3 of saliva for the almond flour and almond micro-particles respectively.  The samples were then fed into a dynamic gastric model, a model which mimics the physical and chemical conditions of the human stomach and small bowel, to assess the digestibility of the nutrients for 63 minutes (the time calculated for digestion in humans). 

The team also carried out a human study during 2 days using a volunteer who had a stoma bag. On the first study day the participant was given 220g of either the almond micro particle muffin or the almond flour muffin with custard for breakfast, a lunch and a dinner. Blood samples were taken and analysed. Effluent samples were collected at 2 hours intervals for 10 hours.

The team note that whilst the in-vivo model only involved one participant "it was still possible to tentatively compare the models in terms of the proportion of lipid released from the matrix and the microstructural changes during digestion and indeed the results showed very good agreement for both outcomes." Grassby et al. report around a 40% difference in total lipid digestibility between the flour and micro particles matrix.  Results from the dynamic gastric model indicate that over 40% of the total fat content was released from the almond flour muffins compared to under 6% in the micro-particle muffins, whilst the in-vivo model showed 97% of the fats released from almond flour muffins and 60% fat from the micro particle muffins. The almond flour muffins also "produced an attenuated, but prolonged plasma glucose response which may be due to more bio-accessible lipid being present in the muffin matrix."

In conclusion, the team report that decreasing the size of particles and the proportion of intact cells, increased the amount of fat digested by in vitro and in-vivo methods. The study demonstrate how processing appears to affects fat absorption from plant-based foods, in particularly almonds.

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